Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Cash flows from operating activities:
Net loss			$ (110,676)	$ (131,358)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation			20,860	25,483
Depreciation and amortization			6,205	7,199
Net amortization/accretion on investment securities			(2,477)	(4,998)
Impairment of long-lived assets	$ 2,382	$ 4,989	2,382	4,989
Non-cash rent expense			2,277	2,694
Non-cash collaboration revenue - related party			0	(14)
Share of loss from equity method investments			0	554
Changes in operating assets and liabilities:
Deposit placed in escrow			(2,711)	(21,429)
Prepaid expenses and other current assets			1,242	(1,953)
Other long-term assets			(1,503)	2,122
Accounts payable			(758)	6,690
Accrued and other current liabilities			(3,488)	(6,670)
Operating lease liabilities			(3,759)	(2,845)
Other long-term liabilities			447	49
Net cash used in operating activities			(91,959)	(119,487)
Cash flows from investing activities:
Purchases of property and equipment			(143)	(8)
Proceeds from maturities of investments			110,300	220,493
Purchase of investments			(60,146)	(123,739)
Net cash provided by investing activities			50,011	96,746
Cash flows from financing activities:
Proceeds from CIRM award (Note 5)			6,908	2,280
Proceeds from issuance of common stock upon exercise of stock options			0	813
Proceeds from issuance of common stock under the employee stock purchase plan			638	856
Net cash provided by financing activities			19,062	110,253
Net change in cash and cash equivalents and restricted cash			(22,886)	87,512
Cash and cash equivalents and restricted cash — beginning of period			85,510	93,447	$ 93,447
Cash and cash equivalents and restricted cash — end of period	$ 62,624	$ 180,959	62,624	180,959	$ 85,510
Non-cash operating activities:
Right-of-use asset obtained in exchange for lease liability			0	2,409
Property and equipment purchases in accounts payable and accrued liabilities			215	0
Non-cash deferred revenue and other long-term liabilities			3,079	3,079
Supplemental disclosure:
Cash paid for amounts included in the measurement of lease liabilities			(6,518)	(6,173)
ATM Offering
Cash flows from financing activities:
Proceeds from issuance of common stock from ATM offering, net of commissions and issuance costs			11,516	1,021
Public offering
Cash flows from financing activities:
Proceeds from issuance of common stock from ATM offering, net of commissions and issuance costs			$ 0	$ 105,283